<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>while循环</title>
</head>
<body>
 <p>点击下面的按钮，只要i小于5就一直循环代码块。</p>
 <button onclick="myFunction()">点击这里</button>
 <p id="demo"></p>
<script>
    function myFunction(){
        var x="",i=0;
        do{
            x=x+"该数字为"+i+"<br>";
            i++;
        }
        while (i<5)
        document.getElementById("demo").innerHTML=x;

    }
</script>
</body>
</html>